One of the key building blocks used in the synthesis of the compound of formula III are enantiomerically pure 2-amino-[5-(1,2-dihydroxy-ethyl)]-pyrazine derivatives of the formula
wherein R is lower alkylcarbonyl or an amino protecting group. For the preparation of active pharmaceutical ingredients (APIs) it is absolutely necessary to use isomerically pure building blocks and/or highly stereoselective procedures, because side components in APIs may have adverse effects in the treatment of illnesses. Therefore, a high purity is requested for all APIs.